U.S. patent application number 09/986604 was filed with the patent office on 2003-05-15 for infra-sound surveillance system.
Invention is credited to Pieper, Norbert.
Application Number | 20030090377 09/986604 |
Document ID | / |
Family ID | 25532587 |
Filed Date | 2003-05-15 |
United States Patent
Application |
20030090377 |
Kind Code |
A1 |
Pieper, Norbert |
May 15, 2003 |
INFRA-SOUND SURVEILLANCE SYSTEM
Abstract
The invention is a method for monitoring an environment by
evaluating an infrasonic signal obtained from said environment. The
method includes averaging said infrasonic signal (V.sub.infra) to
provide an averaged infrasonic signal (V.sub.av), mapping said
averaged infrasonic signal (V.sub.av) according to a function to
provide an infrasonic noise signal (V.sub.noise); averaging said
infrasonic noise signal (V.sub.noise) to provide an averaged
infrasonic noise signal (V.sub.av noise); offsetting said averaged
infrasonic noise signal (V.sub.av noise) with an offset value to
provide an infrasonic level signal (V.sub.limit); comparing said
infrasonic level signal (V.sub.limit) with said averaged infrasonic
signal (V.sub.av); and generating a trigger signal (30) if said
averaged infrasonic signal (V.sub.av) is greater than said
infrasonic level signal (V.sub.limit).
Inventors: |
Pieper, Norbert; (Olfen,
DE) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Family ID: |
25532587 |
Appl. No.: |
09/986604 |
Filed: |
November 9, 2001 |
Current U.S.
Class: |
340/566 ;
340/565; 367/93 |
Current CPC
Class: |
G08B 13/1681 20130101;
G08B 29/24 20130101 |
Class at
Publication: |
340/566 ; 367/93;
340/565 |
International
Class: |
G08B 013/00 |
Claims
1. Method for monitoring an environment by evaluating an infrasonic
signal obtained from said environment, comprising: averaging said
infrasonic signal (V.sub.infra) to provide an averaged infrasonic
signal (V.sub.av), mapping said averaged infrasonic signal
(V.sub.av) according to a function to provide an infrasonic noise
signal (V.sub.noise), averaging said infrasonic noise signal
(V.sub.noise) to provide an averaged infrasonic noise signal
(V.sub.av noise), offsetting said averaged infrasonic noise signal
(V.sub.av noise) with an offset value to provide an infrasonic
level signal (V.sub.limit), comparing said infrasonic level signal
(V.sub.limit) with said averaged infrasonic signal (V.sub.av) and
generating a trigger signal (30) if said averaged infrasonic signal
(V.sub.av) is greater than said infrasonic level signal
(V.sub.limit).
2. Method according to clam 1, wherein a signal is filtered through
a filter (S2.1, S3.1) to provide said infrasonic signal
(V.sub.infra) and wherein a filter characteristic is limited to an
infrasonic frequency range.
3. Method according to claim 1, wherein said averaging of
infrasonic signal to provide an averaged infrasonic signal is a
root mean square averaging (S2.2).
4. Method according to claim 1, wherein said function is
additionally rated with said averaged infrasonic noise signal
(V.sub.av noise) to provide said infrasonic noise signal
(V.sub.noise).
5. Method according to claim 1, wherein said function is a
non-linear function (NLF).
6. Method according to claim 1, wherein said function maps a result
of a combination of said averaged infrasonic signal (V.sub.av) and
said averaged infrasonic noise signal (V.sub.av noise) to provide
said infrasonic noise signal(V.sub.noise).
7. Method according to claim 1, wherein said function maps a result
of a division of said averaged infrasonic signal (V.sub.av)and said
averaged infrasonic noise signal (V.sub.av noise) to provide said
infrasonic noise signal (V.sub.noise).
8. Method according to claim 1, wherein said function maps a result
of a division of said averaged infrasonic signal (V.sub.av) and
said averaged infrasonic noise signal (V.sub.av noise) and a result
of said function is multiplied with said averaged infrasonic noise
signal (V.sub.av noise) to provide said infrasonic noise signal
(V.sub.noise).
9. Method according to claim 1, wherein said offset value is an
absolute offset value.
10. Method according to claim 1, wherein said offset value is a
relative offset value, wherein said relative offset value (20) is
relative to said averaged infrasonic noise signal.
11. Method according to claim 1, wherein said offset value is a
multiplied averaged infrasonic noise signal (V.sub.av noise) for
rating said averaged infrasonic noise signal (V.sub.av noise) to
provide said infrasonic level signal (V.sub.limit).
12. Method according to claim 1, wherein said offset value is
adjustable.
13. Software tool for monitoring an environment by evaluating an
infrasonic signal, comprising program code portions for carrying
out the operations of anyone of claim 1 to 12 when said program is
implemented in a computer program.
14. Computer program for monitoring an environment by evaluating an
infrasonic signal, comprising program code portions for carrying
out the operations of anyone of claim 1 to 12 when said program is
executed on a computer, a processing device or a digital signal
processor.
15. Computer program product for monitoring an environment by
evaluating an infrasonic signal, comprising program code portions
stored on a computer readable medium for carrying out the
operations of anyone of claims 1 to 12 when said program product is
executed on a computer, a processing device or a digital signal
processor.
16. Module for monitoring an environment by evaluating an
infrasonic signal, comprising: a first averaging component for
averaging said infrasonic signal (V.sub.infra) to provide an
averaged infrasonic signal (V.sub.av), a mapping component for
mapping said averaged infrasonic signal (V.sub.av) according to a
function to provide an infrasonic noise signal (V.sub.noise), a
second averaging component for averaging said infrasonic noise
signal (V.sub.noise) to provide an averaged infrasonic noise signal
(V.sub.av noise), an offsetting component for offsetting said
averaged infrasonic noise signal (V.sub.av noise) with an offset
value to provide an infrasonic level signal (V.sub.limit), a
comparing component for comparing said infrasonic level signal
(V.sub.limit) with said averaged infrasonic signal (V.sub.av) and a
generating component for generating a trigger signal if said
averaged infrasonic signal (V.sub.av) is greater than said
infrasonic level signal (V.sub.limit).
17. Module according to claim 16, comprising a filter component
(S2.1, S3.1) for filtering a signal to provide said infrasonic
signal (V.sub.infra) and wherein said filter characteristic is
limited to an infrasonic frequency range.
18. Module according to claim 16, wherein said first averaging
component is a root mean square averaging component (S2.2).
19. Module according to claim 16, wherein said mapping component
comprises additionally a rating component for rating said function
with said averaged infrasonic noise signal (V.sub.av noise) to
provide said infrasonic noise signal (V.sub.noise).
20. Device for monitoring an environment by evaluating an
infrasonic signal, comprising: a detector (10) to detect sound
waves adapted to a frequency range including an infrasonic
frequency range, components responsive to a trigger signal (30,
30.1, 30.2) and a processing unit (200), wherein said processing
unit carries out the operations of a method of a surveillance
system for monitoring by evaluating an infrasonic signal according
to anyone of the claims 1 to 12 and wherein said trigger signal is
generated according to said method.
21. Device according to claim 20, wherein said detector is a
microphone (10).
22. Device according to claim 21, wherein said microphone (10) is
adapted to detect infrasonic signals and voice/speech audio
signals.
23. Device according to claim 20, wherein said device is a radio
frequency phone (300) operating according to a mobile communication
system
24. Device according to claim 20, wherein said device is a
voice/speech controlled device.
25. Surveillance system for monitoring an environment by evaluating
an infrasonic signal, comprising: a module (100) for monitoring by
evaluating an infrasonic signal according to anyone of the claims
16 to 19 and a device (300) processing voice/speech audio and
infrasonic signals comprising: a detector to detect sound waves
adapted to a frequency range including an infrasonic frequency
range and components (5.9, 5.6, 5.61, 5.62) responsive to a trigger
signal, wherein said trigger signal is generated by said
module.
26. System according to claim 25, wherein said detector is a
microphone (10).
27. System according to claim 25, wherein said microphone (10) is
adapted to detect infrasonic signals and voice/speech audio
signals.
28. System according to anyone of the claims 25 to 27 wherein said
device is a radio frequency phone (300) operating according to a
mobile communication system
29. System according to claim 25, wherein said device is a
voice/speech controlled device.
Description
[0001] The present invention relates to a method, a module, a
device, a module and a system for detecting an environment noise by
evaluating an infrasonic signal. Particularly, the method according
to the present invention provides a continuous level adjustment
algorithm to adapt the detection level to a noise background for
evaluating the infrasonic signal, for example to monitor a certain
ambiance or environment.
[0002] Sound frequencies in a frequency range of about 0.1 Hz up to
20 Hz are normally designated as infra-sound. Infra-sound or an
infrasonic pulse is generated by small changes of the air pressure,
respectively. Such small changes of the air pressure may be
generated by opening or closing of a door or a window but even by
persons moving though a room. Due to the object surfaces moving
through the air small changes of the air pressure are released such
that infrasonic pulses are emitted by the respective moving object.
These infrasonic pluses or infra-sound may by detected in a radius
of up to 50 m away from the emerging object. But the radius of
detection is further dependent on background noise and the space
within which the infra-sound is propagating.
[0003] To detect infra-sound special microphones are used. These
microphones are adapted to detect low frequency sound since low
frequency sound is additionally often of low amplitude or low
power, respectively. Nevertheless, microphones able to detect
infra-sound (about 0.1 Hz to 20 Hz) and speech (about 200 Hz to 15
kHz) are available at reliable detection sensitivity.
[0004] A couple of detector systems and devices are in use to
protect environments, rooms, homes, buildings and cars from being
accessed in an unauthorised way. The mainly used detectors are
ultrasonic motion detectors, infra-red detectors, light barriers
and the like. These detectors may be combined with an alarm system
in order to secure a respective object. Also infra-sound detectors
are able to monitor a space signalising an opening of a door or a
window or even a motion within the monitored space. Such
infra-sound detectors are well known and used in motor vehicles to
trigger an alarm system for example to prevent burglary of the
motor vehicles.
[0005] Applications are known where separate infra-sound detecting
devices are connected to a mobile phone, like described in WO
99/53456. These infra-sound detecting devices are used to trigger
or rise any kind of alarm or monitoring action.
[0006] Normally, special infra-sound detecting microphones are used
for detecting infra-sound events. These infra-sound microphones are
expensive and require the implementation of a separate infra-sound
microphone. The usage of microphones detecting sound in a wide
frequency range covering infra-sound frequencies and voice/speech
frequencies enables to extend the devices processing voice/speech
audio signals to an alarm system by operating these devices to
evaluate infrasonic signals detected by the microphones.
[0007] An object of the invention is a method for monitoring an
environment by evaluating an infrasonic signal taking a sound of
said environment. The object is attained by claim 1 and
accompanying dependent claims.
[0008] Another object of the invention is a module of a
surveillance system for monitoring the environment by evaluating an
infrasonic signal. The object is attained by claim 16 and
accompanying dependent claims.
[0009] A further object of the invention a device of a surveillance
system for monitoring by evaluating an infrasonic signal. The
object is reached by claim 20 and accompanying dependent
claims.
[0010] Yet another object of the invention a system of a
surveillance system for monitoring by evaluating an infrasonic
signal. The object is reached by claim 25 and accompanying
dependent claims.
[0011] Usually, infra-sound detection systems, especially used in
combination with alarm systems, employ fixed detection levels. The
detection level defines an infra-sound level, normally an
infra-sound amplitude level, at which a detected infra-sound event
is interpreted as event to be signalised for example by an alarm of
the alarm system. The fixed detection level is often adjustable to
the environmental noise background but the environmental noise
background can change due to outer effects. For example, while
monitoring the infra-sound within a motor vehicle the monitored
infra-sound background level is depending on the place where the
motor vehicle is parked. Near a heavily used road the infra-sound
background level may be higher than within a residential area. That
means, that in case of a low detection level a lot of false alarms
are triggered or in case of a high detection level a careful
opening of a door might be unnoticed. Both cases are undesired.
[0012] Therefore, a continuous level adjustment algorithm provides
the possibility to pre-determine a detection level which is
continuously adapted to the background level. The number of false
alarm of an alarm system which uses this algorithm to evaluate
measured infra-sound can be reduced while the overall sensitivity
of the infra-sound event detection is quite low and hence
reliable.
[0013] According to a first aspect of the invention a method of a
surveillance system for monitoring by evaluating an infrasonic
signal is provided. An infrasonic signal is averaged to yield an
averaged infrasonic signal. The averaged infrasonic signal is
mapped according to a function to yield an infrasonic noise signal.
This infrasonic noise signal is averaged to yield an averaged
infrasonic noise signal. By offsetting the averaged infrasonic
noise signal with an offset value an infrasonic level signal is
provided. This infrasonic level signal is compared with the
averaged infrasonic signal. According to the comparison if the
averaged infrasonic signal is greater than the infrasonic level
signal a trigger signal is generated.
[0014] The infrasonic signal may be provided by filtering. The
filtering may be employed on signals comprising infrasonic signals
and non-infrasonic signals, i.e. signals of non-infrasonic
frequency. Hence, the characteristic of the filtering may be
limited to an infrasonic frequency range. The filtering may be a
band-pass filter employed to extract an infrasonic signal. The
band-pass filter characteristic may be limited to an infrasonic
frequency range. A low-pass filter may also be employed for
extracting the infrasonic signal. Accordingly, the low-pass filter
characteristic may be limited to an infrasonic frequency range.
[0015] The averaged infrasonic signal may be a root mean square
infrasonic signal. But also further averaging methods may be
employed on the infrasonic signal to yield the averaged infrasonic
signal.
[0016] The mapping of the averaged infrasonic signal may also
comprise an additional rating of the function result with the
averaged infrasonic noise signal. The function for mapping may be a
non-linear function. This function may be used for weighting an
additional rating signal, especially the averaged infrasonic noise
signal. The function argument may by the result of an arbitrary
combination of the averaged infrasonic signal and the averaged
infrasonic noise signal. Particularly, the argument may be the
result of the division of the averaged infrasonic signal and the
averaged infrasonic noise signal. Moreover, the function may map
the result the division of the averaged infrasonic signal and the
averaged infrasonic noise signal to provide a function result and
this function result may be multiplied with the averaged infrasonic
noise signal to provide the infrasonic noise signal.
[0017] The offset value may be an absolute offset value, increasing
the averaged infrasonic noise signal by a constant absolute value.
The offset value may be a relative offset value. The increasing
offset of the averaged infrasonic noise signal is determined
relatively to the averaged infrasonic noise signal. Further, the
offset value may be multiplied with the averaged infrasonic noise
signal to provide the infrasonic level signal. Particularly, the
offset value may be defined by a signal-to-noise ratio (SNR).
Moreover, the offset value may be adjustable to adapt the
evaluation method to different operating conditions.
[0018] According to another aspect of the invention a software tool
of a surveillance system for monitoring by evaluating an infrasonic
signal is provided. The software tool comprises program potions for
carrying out the operations of the aforementioned methods of a
surveillance system for monitoring by evaluating an infrasonic
signal when the software tool is implemented in a computer program
and/or executed on a computer, a processing device or a digital
signal processing device.
[0019] According to another aspect of the invention a computer
program of a surveillance system for monitoring by evaluating an
infrasonic signal is provided. The computer program comprises
program potions for carrying out the operations of the
aforementioned methods of a surveillance system for monitoring by
evaluating an infrasonic signal when the software tool is
implemented in a computer program and/or executed on a computer, a
processing device or a digital signal processing device.
[0020] According to another aspect of the invention a computer
program product is provided which comprises program code portions
stored on a computer readable medium for carrying out the
aforementioned methods of a surveillance system for monitoring by
evaluating an infrasonic signal when said program product is
executed on a computer, a processing device or a digital signal
processing device.
[0021] According to another aspect of the invention a module of a
surveillance system for monitoring by evaluating an infrasonic
signal is provided. The module comprises a first averaging
component for averaging the signal to provide an averaged
infrasonic signal, a mapping component for mapping the averaged
infrasonic signal according to a function to provide an infrasonic
noise signal, a second averaging component for averaging the
infrasonic noise signal to provide an averaged infrasonic noise
signal, an offsetting component for offsetting the averaged
infrasonic noise signal with an offset value to provide an
infrasonic level signal, a comparing component comparing the
infrasonic level signal with the averaged infrasonic signal and a
generating component generating a trigger signal if the averaged
infrasonic signal is greater than the infrasonic level signal.
[0022] The module may also comprise a filter component for
filtering the infrasonic signal. The filter component may be
employed on signals comprising infrasonic signals and
non-infrasonic signals, i.e. signals of non-infrasonic frequency.
For filtering the infrasonic signal the filter component
characteristic may be limited to an infrasonic frequency range. It
may be possible to employ a band-pass filter or a low-pass filter
on the infrasonic signal.
[0023] The averaging component may be a root mean square averaging
component to provide a root mean square infrasonic signal as
averaged infrasonic signal.
[0024] The mapping of the averaged infrasonic signal may also
comprise an additional rating of the function result with the
averaged infrasonic noise signal. Therefore, the module may also
comprise a rating component for rating the function with the
averaged infrasonic noise signal. The function for mapping may be a
non-linear function. This function may be used for weighting an
additional rating signal, especially the averaged infrasonic noise
signal. The function argument may by the result of an arbitrary
combination of the averaged infrasonic signal and the averaged
infrasonic noise signal. Particularly, the argument may be the
result of the division of the averaged infrasonic signal and the
averaged infrasonic noise signal. Therefore, the module may
comprise a dividing component for the averaged infrasonic signal
and the averaged infrasonic noise signal. Moreover, the function
may map the result the division of the averaged infrasonic signal
and the averaged infrasonic noise signal to provide a function
result and this function result may be multiplied with the averaged
infrasonic noise signal to provide the infrasonic noise signal.
[0025] The offset value may be an absolute offset value, increasing
the averaged infrasonic noise signal by a constant absolute value.
The offset value may be a relative offset value. The increasing
offset of the averaged infrasonic noise signal is determined
relatively to the averaged infrasonic noise signal. Further, the
offset value may be offset by multiplying with the averaged
infrasonic noise signal to provide the infrasonic level signal.
Particularly, the offset value may be defined by a signal-to-noise
ratio (SNR). Moreover, the offset value may be adjustable to adapt
the evaluation method to different operating conditions.
[0026] According to another aspect of the invention a device of a
surveillance system for monitoring by evaluating an infrasonic
signal is provided. The device comprises a detector to detect sound
waves, a processing unit and components responsive to a trigger
signal. The detector is adapted to a sound wave frequency range
including an infrasonic frequency range. The processing units
executes the operation of the aforementioned method of a
surveillance system for monitoring by evaluating an infrasonic
signal and the infrasonic signal is provided by the detector. The
trigger signal is generated according to the aforementioned method
and initiates operations and functions of the device. The detector
signals may have to be filtered to extract infrasonic signals out
of the detector signals.
[0027] The detector able to detect infrasonic signals may be a
microphone. The microphone may be adapted to an infrasonic
frequency range. Further, the microphone may be adapted to an
infrasonic frequency range and a frequency range of audio signals
occurring in voice or speech.
[0028] The device may be a mobile phone. The mobile phone may be a
mobile phone built-in a motor vehicle. Mobile phones include
digital signal processing units to operate on voice signals of the
user. These digital processing units may also operate the
evaluation of the infrasonic signals. Therefore, it may be
necessary that each mobile phones provide microphones which are
able to detect both infrasonic signals and voice/speech
signals.
[0029] The device may be a voice/speech controlled device. Device
functions of such devices may be controlled by spoken commands.
Therefore, the devices may each have to comprise a voice signal
processing unit. This voice signal processing unit may also operate
the evaluation of the infrasonic signals. Therefore, it may be
necessary that the devices include microphones which are able to
detect both infrasonic signals and voice/speech signals.
[0030] According to another aspect of the invention a system of a
surveillance system for monitoring by evaluating an infrasonic
signal is provided. The system comprises a module according to the
aforementioned module of a surveillance system for monitoring by
evaluating an infrasonic signal and a device processing
voice/speech signals and infrasonic signals. This device comprises
a detector to detect sound waves and components responsive to a
trigger signal. The detector is adapted to a sound wave frequency
range including an infrasonic frequency range. The trigger signal
is provided by the module. The detector signals may have to be
filtered to extract infrasonic signals out of the detector
signals.
[0031] The detector able to detect infrasonic signals may be a
microphone. The microphone may be adapted to an infrasonic
frequency range. Further, the microphone may be adapted to an
infrasonic frequency range and a frequency range of audio signals
occurring in voice or speech sound signals.
[0032] The device may be a mobile phone. The mobile phone may be a
mobile phone built-in a motor vehicle. Mobile phones include
digital signal processing units to operate on voice signals of the
user. These digital processing units may also operate the
evaluation of the infrasonic signals. Therefore, it may be
necessary that the mobile phones provide microphones which are able
to detect both infrasonic signals and voice/speech signals.
[0033] The device may be a voice/speech controlled device. Device
functions of such devices may be controlled by spoken commands.
Therefore, the devices may each have to comprise a voice signal
processing unit. This voice signal processing unit may also operate
the evaluation of the infrasonic signals. Therefore, it may be
necessary that the devices include microphones which are able to
detect both infrasonic signals and voice/speech signals.
[0034] The invention will now be described in more detail with
reference made to the accompanying drawings, in which:
[0035] FIG. 1a shows a flow diagram of the operations for
evaluating an infrasonic signal according to an embodiment of the
invention,
[0036] FIG. 1b shows a flow diagram of the continuous level
adjustment algorithm according to FIG. 1a,
[0037] FIG. 2 shows a plot illustrating a non-linear function
according to the continuous level adjustment algorithm with respect
to an embodiment of the invention,
[0038] FIG. 3 shows a time plot of an infra-sound measurement
illustrating the evaluation according to the continuous adjustment
algorithm with respect to an embodiment of the invention,
[0039] FIG. 4 shows a schematic diagram of audio signal processing
device equipped with a microphone and extended to evaluate an
infrasonic signal according to an embodiment of the invention
and
[0040] FIG. 5 shows an implementation of the infra-sound detection
device within a digital signal processor of a mobile phone with
respect to an embodiment of the invention and
[0041] FIG. 6 shows a mobile phone with implemented infra-sound
detection according to an embodiment of the invention.
[0042] Same or equal parts shown in the figures will be referred by
the same reference numerals.
[0043] The evaluation process of the infrasonic signals provides
the possibility to extract infrasonic signals out of the noise
background or environmental noise. Since the infrasonic signals may
be measured signals background noise is always present within the
measured signals. For example, especially in case of the
utilisation of an infrasonic detector for monitoring a certain
space, like a room of a spacious interior of a motor vehicle or a
building a lot of infrasonic signals are detected. The extraction
of conspicuous infrasonic signals provide the possibility to
monitor effectively a spacious interior which means that the number
of false event detection is as small as possible and only
reasonable events are reported.
[0044] The evaluation process is based on a suitable algorithm for
extracting infrasonic signals. The evaluation process distinguishes
itself by a continuous adaptation of a noise level determined for
the infrasonic signal. This adaptation enables to extract
infrasonic signals even if the noise background is changing in
time.
[0045] An additional provided offset value may define and provided
to the continuous level adjustment. The continuous level adjustment
determines an averaged infrasonic noise level representing the an
averaged value of the background noise which is included in the
infrasonic signal. A threshold value may be determined based on the
offset value and the averaged infrasonic noise signal. The
threshold level may be used for evaluating an infrasonic signal by
comparing, i.e. infrasonic signals greater than the threshold value
may be extracted infrasonic signals of relevant values or strength
by the evaluation process, respectively, which enables to generate
a trigger in combination with this extraction process.
[0046] FIG. 1a shows a flow diagram of the operations for
evaluating an infrasonic signal according to an embodiment of the
invention.
[0047] In an operation S1.1 an infrasonic signal V.sub.infra is
provided. The infrasonic signal V.sub.infra may be a signal of an
infra-sound detector. The infra-sound detector may be a microphone
adapted to frequencies out of the infrasonic frequency range.
[0048] It may also be possible to obtain the infrasonic signal from
a microphone adapted to frequencies out of the infrasonic frequency
range and audio frequencies. Most standard microphone adapted to
audio frequencies and used for detecting audio signals have the
possibility to detect infrasonic signals. The sensitivity of these
microphones in the frequency range of infra-sound may be lower
since these microphone are not optimised for detecting infra-sound
but may even enable to obtain and evaluate the infrasonic signals.
It may be necessary to amplify the signals using an adapted
suitable amplifier.
[0049] Further it may be necessary to filter the infrasonic
signals. Particularly in case of using microphones adapted to a
wide frequency range covering non-infrasonic frequencies an adapted
filtering may have to be employed. Due to the kind of detector used
for obtaining the infrasonic signals, a band-pass filter or a
low-pass filter may be employed on the signals of the detector to
obtain suitable infrasonic signals which can be evaluated according
to an embodiment of the present invention. The characteristic of
the filter may have to be adapted to the infrasonic frequency range
or a part thereof.
[0050] In an operation S1.2 the infrasonic signal V.sub.infra may
be averaged. The averaging may be any kind of averaging method.
Further, a root mean square averaging may be possible. The
averaging procedure results in an averaged infrasonic signal
V.sub.av.
[0051] In an operation S1.3 an infrasonic level signal V.sub.limit
is obtained from the averaged infrasonic signal V.sub.av. The
averaged infrasonic signal V.sub.av is obtained according to the
continuous level adjustment (FIG. 1b). The continuous level
adjustment provides a method to obtain an adapted noise level of a
noise background of the infrasonic signal, which means that the
adapted noise level is always adapted to the noise background even
if the noise background is changing on a certain time scale. This
adapted noise level is rated with an additional offset value which
is provided to the continuous level adjustment. The adapted noise
level may be rated with this additionally provided offset value to
provide the infrasonic level signal.
[0052] The adapted noise level may represent a kind of mean noise
background level with respect to a certain time scale. The rating
of the adapted noise level with the offset value may be understood
as increasing the adapted level by an offset value to obtain the
infrasonic level signal V.sub.limit. Thus the infrasonic level
signal V.sub.limit defines a level signal which extends timely
parallel to a noise background adapted level offset by an
additional offset value.
[0053] The additional offset value is adjustable to define the
sensitivity of the evaluation of the infrasonic signal. The
adjustability provides the possibility to select an offset value
according to the application. Referring again to the above
mentioned example, in case of monitoring a spacious interior of a
motor vehicle the background noise is more intensive and more
varying on a short and long time scale as in case of monitoring a
spacious interior of a building. A noise background varying on a
long time scale is covered by the above described continuous level
adjustment. A noise background varying on a short time scale may be
covered by an adjusted offset value.
[0054] The offset value may be an absolute offset value.
[0055] The offset value may define a relative offset value, i.e.
the adapted noise level is offset by an offset value which is
relative to the adapted noise level according to the offset value
to provide the infrasonic noise signal V.sub.limit. Further, that
means that the higher the noise background the higher the offset
value, whereas the offset value is small in case of a small noise
background.
[0056] It may be possible to provide a signal-to-noise ratio (SNR)
20 as the offset value to the continuous level adjustment. A SNR 20
is a relative value, i.e. the SNR 20 may be a factor with which the
adapted noise level is rated or multiplied, respectively. A
signal-to-noise ratio is a value known to those skilled in the art
for defining usually a minimal signal level with respect to the
noise background at which signal may be properly distinguished and
evaluation of signals may be meaningful.
[0057] In an operation S1.4 the averaged infrasonic signal V.sub.av
and the infrasonic level signal V.sub.limit are compared. If the
averaged infrasonic signal V.sub.av is greater than the infrasonic
level signal V.sub.limit a trigger signal may be initiated. It may
also be possible to initiate a trigger signal if the averaged
infrasonic signal V.sub.av is grater than or equal to the
infrasonic level signal V.sub.limit.
[0058] It may be possible to provide a pre-defined trigger signal
in order to control further operations, devices, units or functions
which may be operated in case of a trigger event. Further it may
also be possible to provide the averaged infrasonic signal V.sub.av
itself as trigger signal which may be processed by further
operations, devices, units or functions.
[0059] The continuous level adjustment algorithm is used to
determine a threshold level, namely infrasonic level signal
V.sub.limit, will be described in more details. The continuous
level adjustment may allow to determine an averaged infrasonic
noise signal which corresponds to the background noise or
environmental noise of the infrasonic signal, respectively.
[0060] The origin of the noise background may be reduced to
different noise sources. One of the sources may be infrasonic
background signals detected and determined by the infrasonic
detector. These signals may are based on physical processes in the
detection space of the infrasonic detector. Moreover also
infrasonic signals which may be traced back to dedicated events but
which may not wished to be detected and evaluated may be also
termed as background noise. Further, the infrasonic detector may
generate itself infrasonic signal due to the detection method or
process, respectively, known to all detectors based on physical
measurement processes. Also, interposed signal processing
components may modify or contribute to the background noise.
[0061] The enumeration of the background sources described above
may not be complete. Further background generating processes may be
involved and contribute in any way to the complete background noise
or background signal, respectively, known to those skilled in the
art.
[0062] The continuous level adjustment may also compensate
sensitivity differences of infrasonic detectors and components
processing the obtained infrasonic signals by the infrasonic
detector and interposed between infrasonic detector and evaluation
process of the infrasonic signals. These components, not limiting,
may be signal amplifiers, signal filters and the like. Properties
of detectors as also signal processing components may vary within
the series. This may lead to an overall different signal
sensitivity due to the variation and/or to different background
noise contributions. The continuous level adjustment according to
an embodiment of the present invention may be able to compensate
such effects and allow to evaluate infrasonic signals in a
comparable way by different implementations of the signal
evaluation process in case of using components with varying
properties.
[0063] FIG. 1b shows a flow diagram of the continuous level
adjustment algorithm according to FIG. 1a. Further, additional
references to FIG. 1a will be provided to enlighten broadly the
method for evaluating an infrasonic signal with respect to an
embodiment of the invention.
[0064] In an operation S16 an averaged infrasonic signal V.sub.av
is provided. According to the FIG. 1a This signal is provided by
operation S1.2.
[0065] The following operations S1.7, S1.8 and S.19 may describe
the continuous level adjustment referred as operation S1.3 in FIG.
1a in detail.
[0066] In an operation S1.7 an infrasonic noise signal V.sub.Noise
is determined from an averaged infrasonic noise signal V.sub.av
noise representing the level of the infrasonic background noise and
the averaged infrasonic signal V.sub.av. A non-linear weighting
function (NLF) may be employed to weight the averaged infrasonic
signal in comparison to the averaged infrasonic noise signal
V.sub.av noise. The result of the non-linear weighting function
(NLF) is used for rating the averaged infrasonic noise signal
V.sub.av noise, i.e. if the averaged infrasonic signal V.sub.av is
equal to the averaged infrasonic noise signal V.sub.av noise the
values of the averaged infrasonic noise signal V.sub.av noise may
be assigned unmodified to the infrasonic noise signal V.sub.Noise.
In case of an averaged infrasonic signal V.sub.av greater than the
averaged infrasonic noise signal V.sub.av noise a value which is
greater than the value of the averaged infrasonic noise signal
V.sub.av noise may be assigned to than infrasonic noise signal
V.sub.Noise. Further, in case of an averaged infrasonic signal
V.sub.av smaller than the averaged infrasonic noise signal V.sub.av
noise a value which is smaller than the value of the averaged
infrasonic noise signal V.sub.av noise may be assigned to than
infrasonic noise signal V.sub.Noise.
[0067] The result of the operation S1.7 may be denoted
mathematically by following term: 1 V Noise = V AV Noise NLF ( V AV
V AV Noise )
[0068] wherein the function NLF may be defined as follows: 2 NLF (
x ) = { y > x for 1 x < 1 1 for x = 1 y < x for 1 <
x
[0069] This definition of the non-linear function NLF may fulfil
the weighting of the averaged infrasonic noise signal in an
adequate way.
[0070] In an operation S1.8 the infrasonic noise signal V.sub.av is
averaged by a suitable and adapted averaging method to provide the
averaged infrasonic noise signal V.sub.av noise. The averaging
method may be a timely averaging to reduce variations in the
infrasonic noise signal V.sub.av since it is assumed that processes
changing the signal strength of the background noise are occurring
on a time scale which is longer than the time scale of processes
generating infrasonic signals which are desired to be extracted in
order to initiate the trigger as a result of the comparison
operation in operation S1.5 in FIG. 1a. The operation may provide
the averaged infrasonic noise signal V.sub.av noise.
[0071] It may be noted that the continuous level adjustment
according to an embodiment of the present invention is an iterative
method for obtaining an averaged infrasonic noise signal V.sub.av
noise. In the beginning the averaged infrasonic noise signal is
unknown in the operation S1.7 since this signal may be provided by
operation S1.8 for the first time. A suitable adapted initial
signal value assigned to the unknown averaged infrasonic noise
signal V.sub.av noise, for example the averaged infrasonic signal
value (V.sub.av) may be assigned to the averaged infrasonic noise
signal V.sub.av noise, and a suitable adapted defined non-linear
function NLF may ensure that the continuous level adjustment
converge against an averaged infrasonic noise signal V.sub.av noise
representing the averaged value of the background noise
signals.
[0072] In an operation S1.9 the averaged infrasonic noise signal
V.sub.av noise may be rated with an offset value to provide the
infrasonic level signal V.sub.limit. The offset value may be an
absolute offset value increasing the averaged infrasonic noise
signal V.sub.av noise by a constant offset value. Further the
offset value may be a relative offset value increasing the averaged
infrasonic noise signal V.sub.av noise by a relative offset value
according to the value of the averaged infrasonic noise signal
V.sub.av noise.
[0073] According to an embodiment of the invention a signal to
ratio value (SNR) 20 may provided as offset value. SNR values are
known to those skilled in the art for defining signal values and
levels in respect to background noise of the respective signal. The
infrasonic level signal V.sub.limit may be based on the SNR value
20 and on the averaged infrasonic noise signal V.sub.av noise
according to the following mathematical term:
V.sub.Limit=V.sub.AV Noise.multidot.SNR
[0074] An additional pre-defined offset value of the continuous
level adjustment may allow to adapt the continuous level adjustment
to different operating conditions associated with different
background noise processes. The fluctuations of the background
signals may be of different magnitude and an adjustable offset
value may allow to adapt to this fluctuations in the background
noise.
[0075] In an operation S1.10 the provided infrasonic level signal
may be provided to further operations and processing functions.
According to an embodiment of the invention and with respect to
FIG. 1a the infrasonic level signal V.sub.limit is provided to
operation S1.4 to be compared with the averaged infrasonic signal
for evaluating V.sub.av and generating of a trigger signal
depending on the comparison result of operation S1.4 in FIG.
1a.
[0076] The presented mathematical terms may not be limiting. These
terms are provided to enlighten the scope and the virtue of the
continuous level adjustment. According to the basic idea of the
continuous level adjustment further embodiments may be
suitable.
[0077] A non-linear function NLF according to the above described
definition of the non-linear function will be given in the
following FIG. 2. This plotted non-linear function NLF is an
exemplary non-linear function out of a plurality of possible
non-linear functions which fulfil the given definition.
[0078] FIG. 2 shows a function plot illustrating a non-linear
function according to the continuous level adjustment algorithm
with respect to an embodiment of the invention.
[0079] The plot depicts a function x=y, denoted as 1:1 transition,
and a non-linear function suitable for operating in the continuous
level adjustment like described above. The argument of the
functions is plotted on the horizontal axis or abscissa,
respectively, whereas the results of the functions is plotted on
the vertical axis or ordinate, respectively. Both axis show a value
range of 1 to 3.
[0080] Referring back to operation S1.7 shown in FIG. 1b, the
argument of the non-linear function is a quotient of the averaged
infrasonic signal V.sub.av and the averaged infrasonic noise signal
V.sub.av noise, i.e. the ratio of the current evaluated signal and
the averaged signal noise. Argument between 0 and 1 means that the
current signal is smaller as the obtained averaged noise of the
infrasonic signal, whereas an argument greater than 1 means
accordingly that the current infrasonic signal is higher as the
obtained averaged noise of the infrasonic signal. The
first-mentioned argument range may be denoted as expansion range
and the last-mentioned argument range may be denoted as compression
range.
[0081] The function x=y or 1:1 transition assigns the arguments
unmodified to the function values, respectively. Hence, the value
of functions depicted above this 1:1 transition are greater than
the value of its respective arguments. Accordingly, the value of
functions depicted above this 1:1 transition are smaller than the
value of its respective arguments. Consequently, the naming
"expansion range" and "compression range" may be understood since
the non-linear function is depicted above and below the 1:1
transition, respectively.
[0082] Employed on the method according to an embodiment of the
invention that means that an averaged infrasonic signal V.sub.av
which is smaller than the averaged infrasonic noise signal V.sub.av
noise is amplified whereas an averaged infrasonic signal V.sub.av
which is greater that the averaged infrasonic noise signal V.sub.av
noise is reduced. First and foremost, a small slope of the
non-linear function within the compression range reduces
considerably high infrasonic signals so that these infrasonic
signals do not affect significantly the determination of the
averaged infrasonic noise signal. The non-linear function may be
used as a weighting non-linear function of the current infrasonic
signal with respect to the averaged infrasonic noise signal.
[0083] Summarising the most important points:
[0084] low volume signal are enhanced, high volume signals,
especially high peak signals are strongly suppressed,
[0085] even extremely high peak of the infrasonic signal will not
have any impact in a way that the generated averaged noise signal
will be increased significantly,
[0086] using the non-linear weighting function allows the use of a
relatively short time for determining the average of the noise
signal,
[0087] the continuous level adjustment is able to adapt relatively
quick to changing noise background without being affected by high
signal peaks.
[0088] The definition of the non-linear function is free. A
concrete function term has to fulfil the conditions of the
expansion range and the compression range. Further conditions are
not made to the non-linear function. The concrete slope of the
non-linear function may be adapted to a special embodiment of the
invention with respect to the conditions under which infrasonic
signals are obtained for a following evaluation.
[0089] In the following an exemplary measurement employing the
above described method for evaluating an infrasonic signal will be
illustrated. Therefore, an embodiment according to the method for
evaluating an infrasonic signal may be implemented to monitor a
sleeping room and to realise a monitoring alarm system. The
monitoring is carried out in a user's sleeping room from
approximately 12 p.m. at the evening to 10 a.m. at the next
morning. Different signals according to the embodiment of the
invention are described.
[0090] FIG. 3 shows a time plot of an infra-sound measurement
illustrating the evaluation according to the continuous adjustment
algorithm with respect to an embodiment of the invention.
[0091] The exemplary measurement of infrasonic signals and the
corresponding averaged infrasonic noise signal V.sub.av noise,
infrasonic level signal V.sub.limit during the monitoring process
are depicted in FIG. 3. The abscissa shows the time at which the
signals are measured and obtained, respectively. The ordinate shows
the value of the signals depicted as decibel units. Signal values
below the averaged infrasonic noise signal V.sub.av noise are not
plotted, only signal values above this value are plotted in FIG.
3.
[0092] The slope of the averaged infrasonic noise signal V.sub.av
noise represents the noise background, denoted as environmental
noise herein. It may be seen that the continuous level adjustment
provides a suitable method the determine the noise background of an
infrasonic signal measurement. This noise background varies over
the measurement time and the averaged infrasonic noise signal
V.sub.av noise follows accordingly these variations.
[0093] The infrasonic level signal V.sub.limit may be obtained by
offsetting the averaged infrasonic noise signal V.sub.av noise with
an offset value, herein a signal-to-noise ration SNR is employed
for offsetting the averaged infrasonic noise signal V.sub.av
noise.
[0094] The single tips of the plotted infrasonic peaks represent
the averaged infrasonic signals V.sub.av, herein a root mean square
averaging is performed to provide the averaged infrasonic signals
V.sub.av in the following denoted as root mean square infrasonic
signals V.sub.RMS. root mean square infrasonic signals V.sub.RMS
within the band limited by the averaged infrasonic noise signal and
the infrasonic level signal may not initiate a trigger signal since
these signals are smaller than the infrasonic level signal.
[0095] The alarm system is switched on with the beginning of the
signal recording of the plot in FIG. 3. Signals indicated with an
indicator A may reference infrasonic signal above the infrasonic
level signal. Accordingly, these signals may have initiated a
generation of a trigger signal. The alarm system may indicate a
significant monitoring signal on such a trigger signal and may rise
alarm. Three events are indicated. The first significant signal
indicated with the indicator A coincidences the event that the user
went to bed. This procedure has generated an infrasonic signal, due
to moving a door, which was detected by the alarm system. The
second event shows an infrasonic signal which was generated by
closing a door and the third event shows an event when the user got
up. Other significant infrasonic signals had not passed the
infrasonic level signal and were therefore not evaluated as
significant signals.
[0096] In order to compare an embodiment according to the invention
with an infrasonic monitoring system of state of the art a second
static alarm level is provided and an infrasonic signal evaluation
is carried out according to this static alarm level. Static alarm
level means that a constant infrasonic level signal is used for
evaluating the measured infrasonic signals wherein the static alarm
level is not adapted to the changing background. The static alarm
level may be seen as a horizontal line in the plot of the measured
infrasonic signal. Single signals which may have initiated an alarm
due to passing the static alarm level are indicated by indicator F.
These events are false alarm events due to the dynamic alarm level
which corresponds to the infrasonic level signal obtained by the
continuous level adjustment.
[0097] Accordingly, the employment of a background adjusted
infrasonic level signal for evaluating infrasonic signals is
advantageous since false alarm event may be prevented. Alarm
systems have to be reliable. The more false alarm events are
generated by the alarm system the more alarm events are ignored
even if the alarm event are reasonable. A rising background noise
may initiate a lot of false alarm events in case of a static alarm
level.
[0098] An embodiment according to the invention determines the
average infrasonic noise signal V.sub.av noise and multiplies that
signal with a sufficient application specific signal-to-noise ratio
SNR. For example a ratio of 6 dB may be a sufficiently best
specific noise to signal ratio for monitoring a single room of a
building/house whereas a ratio of 18 dB may be a sufficiently best
specific noise to signal ratio for monitoring a spacious interior
of a motor vehicle.
[0099] Another advantage of an embodiment according to the method
of the invention may be that a background adapted alarm level may
be effectively smaller than a static alarm level, since a static
alarm level may be set to a static level which ensures that the
number of false alarms is as small as possible. Therefore, the
users of alarm system employing static alarm levels often take more
likely a risk of a higher alarm level and thereupon of undetected
events. The continuous level adjustment allows to overcome this
problem.
[0100] An embodiment according to the invention may comprise an
infrasonic detector to obtain infrasonic signals and an
implementation of the method for evaluating infrasonic signals
thereof. Infrasonic detectors may be adapted to an infrasonic
frequency range or a part of an infrasonic frequency range
according to the application of the embodiment. The infrasonic
frequency range may cover a frequency range of approximately 0.2 Hz
to 20 Hz. This frequency range may not be covered completely by the
infrasonic detectors, for example a frequency range of 2 Hz to 20
Hz may be suitable for monitoring systems like alarm systems.
[0101] Moreover, microphones may be suitable detector devices for
detecting infrasonic signals. Even voice or audio microphones may
be used as infrasonic detectors. The sensitivity of such adapted
microphones may have to be increased by suitable amplifying the
obtained signals. An implementation of an infrasonic detection
system in combination with an evaluation unit according to an
embodiment of the present invention will be described in the
following figures.
[0102] FIG. 4 shows a schematic diagram of audio signal processing
device equipped with a microphone and extended to evaluate an
infrasonic signal according to an embodiment of the invention. A
signal processing device 100 may be provided. The device 100 may
comprise a microphone 10 adapted to detect infrasonic signals 10.2
and audio signal 10.1, especially voice signals. The obtained
signal V.sub.mic may be passed to an evaluation unit 110 for
evaluating the infrasonic signals. The infrasonic signal may have
to be extracted from the audio signal V.sub.mic due to the wide
frequency range of the microphone 10.
[0103] In an operation S2.1 the audio signals V.sub.mic may be
filtered using a filter adapted to an infrasonic frequency range of
part of this frequency range. According to the frequency range and
the properties of the microphone 10, a low-pass or a band-pass
filter may be used for extraction of the infrasonic signals. Both
the low-pass filter characteristic and the band-pass filter
characteristic may have to be limited to the desired infrasonic
frequency range. The filtering of the audio signals V.sub.mic may
yield to the infrasonic signals V.sub.infra.
[0104] In an operation S2.2 the yielded infrasonic signals
V.sub.infra may be averaged. A suitable and preferable averaging of
the infrasonic signals V.sub.infra may be a root mean square
averaging which yields to root means square infrasonic signals
V.sub.RMS.
[0105] In an operation S2.3 an infrasonic level signal V.sub.limit
is determined from the root mean square infrasonic signal V.sub.RMS
by employing the continuous level adjustment as described above in
detail. An additional offset value, herein a signal-to-noise ratio
(SNR) 20 may be provided to the continuous level adjustment of
operation S2.3 to adapt the infrasonic level signal V.sub.limit to
the working conditions of the signal processing device 100,
especially the sensitivity of the infrasonic signal evaluation.
[0106] In an operation S2.4 the root mean square infrasonic signals
V.sub.RMS may be compared with the infrasonic level signal
V.sub.limit determined from the root mean square infrasonic signals
V.sub.RMS and the offset SNR 20. If the root mean square infrasonic
signals V.sub.RMS is grater than the infrasonic level signal
V.sub.limit a trigger signal 30 is generated. The trigger signal 30
may indicate that an infrasonic signal has passed a threshold value
defined by the infrasonic level signal V.sub.limit. Further, the
trigger signal 30 may be employed for triggering further provided
internal or external components which are responsive on this
trigger signal 30. For example, the trigger signal may be used to
initiate an alarm of an alarm system.
[0107] An embodiment comprising microphone 10, evaluation unit 110
and trigger 30 may allow to set up an independent device for
evaluating infrasonic signals. The provided trigger signal may be
connected to further devices, such as alarm system, which may
response suitable on the trigger signal. The embodiment of the
invention according to FIG. 4 may be realised as an electronic
circuit. Preferably, a digital signal processing (DSP) unit may
comprise a software tool or an executable code section for carrying
out the operations. The utilisation of a DSP unit may need an
analog-to-digital converter (ADC) for receiving the analog signals
of a microphone and providing a corresponding digital signal.
[0108] It may also be possible, that the device 100 may comprise
additional units since the microphone 10 may be adapted to audio
frequencies and infrasonic frequencies. The detected and obtained
audio frequencies may be processed in an additional unit 120. It
may be noted that the unit 120 may constitute an arbitrary number
of units for processing signals obtained by the microphone. A
plurality of devices may be appropriate to comprise a plurality of
units processing audio and infrasonic signals which are obtained by
a single adapted microphone. Preferably, the audio processing
device may be a voice or speech processing device, respectively.
Further it may be possible that the built-in microphone is not
adapted to obtain infrasonic signals. Since microphones adapted to
audio frequencies and infrasonic frequencies with an appropriate
sensitivity are available and the exchange of the built-in
microphone may be carried out easily.
[0109] Mobile phones and especially built-in phones in motor
vehicles may provide the possibility to include a unit for
evaluating infrasonic signals for monitoring spaces, especially
spacious interior of a motor vehicle and to serve as alarm system.
Usually, mobile phones comprise a digital signal processing (DSP)
unit for processing voice or speech audio signals, respectively.
This DSP unit may comprise additional a software tool or a code
section according to an embodiment of the invention for evaluating
the infrasonic signals. Moreover, in case of employing a mobile or
built-in phone for monitoring the phone may generate a message
which may be transmitted to the respective owner, to a security
service provider, to the police or the like in response to a
trigger signal generated by the infrasonic evaluation. The message
may be a short message service (SMS) message according to the GSM
standard for mobile communication. According messages services are
provided by other mobile communication systems like UMTS, WCDMA,
DCS etc.
[0110] Further, the phone may automatically call a pre-defined
number to transmit a voice message or to enable the receiver of the
call to listen to the occurrences which initiated the trigger
signal of the infrasonic evaluation, for example enable the
receiver to decide if the infrasonic evaluation initiated a false
or a reliable alarm.
[0111] It may be noted that mobile or built-in phones of motor
vehicles may only an example for the implementation of the
infrasonic evaluation. In the future devices especially devices
integrated in motor vehicles may be controlled by voice or speech
commands, such as voice controlled phones, radio receivers,
navigation systems, air conditioning systems and likely user
controlled equipment. This method of controlling electrical devices
provide a secure and simple controlling method. All this voice and
speech controlled devices require an audio signal detector, for
example a microphone, and an audio signal processing unit. These
voice and speech controlled devices may provide the possibility to
implement an infrasonic evaluating unit according to an embodiment
of the invention.
[0112] Nevertheless, also further processing devices may implement
the method for evaluating infrasonic signals. For example standard
computers or mobile terminal devices comprising or connected to a
microphone able for or adapted to detect infrasonic signals may be
used for evaluating according to an embodiment of the
invention.
[0113] The following figures present embodiments of the present
invention included in a phone for mobile communication. The phone
may be a mobile phone or a built-in mobile phone in a motor
vehicle. According to the description above embodiments may be also
included in further voice controlled and voice processing devices
but which may be not limiting.
[0114] FIG. 5 shows an implementation of the infra-sound detection
device within a digital signal processor of a mobile phone with
respect to an embodiment of the invention. A microphone 10 adapted
to voice audio and infrasonic audio may detect the signals. A
pre-amplifier 11 may amplify the signals and an analog-to-digital
converter (ADC) 12 may convert the microphone detected signals to
digital signals which may be processed by a digital signal
processing unit 200. According to the embodiment of the invention
the microphone signal may be passed to voice audio processing and
to infrasonic audio processing. The digital signal processing unit
200 may provide different signals thereof, an alarm trigger 30.1
generated by. the infrasonic evaluating process and a speech audio
signal 40. The alarm trigger 30.1 may be used to trigger further
units responsive in an appropriate way thereto. The speech audio
signal 40 may be passed to the further units operating speech audio
signal 40 in a mobile phone, like the transmitting unit.
[0115] In an operation S3.1 the infrasonic signal V.sub.infra may
be extracted from the microphone signal V.sub.mic by employing a
band-pass filter limited to the desired infrasonic frequency
range.
[0116] The following operations are described above and shortened
repeated.
[0117] In an operation S2.2 a root mean square averaging of the
infrasonic signal V.sub.infra yields to a root mean square signal
V.sub.RMS.
[0118] In an operation S2.3 the continuous level adjustment yields
to the infrasonic level signal V.sub.limit. A signal-to-noise ratio
SNR 20 may be provided to the continuous level adjustment to adapt
the sensitivity of the infrasonic evaluation.
[0119] In an operation S2.4 the root mean square infrasonic signal
and the infrasonic level signal may be compared yielding to a
trigger signal. The trigger signal may be a signal providing two
trigger levels. A first trigger level may indicate that the root
mean square V.sub.RMS is greater than the determined infrasonic
level signal V.sub.limit and a second trigger level may indicate
the corresponding other case of the signal comparison. A trigger
signal able to comprise two signal levels is indicated in FIG. 5 by
a trigger signal denoted as alarm trigger as "true" 30.1 or by a
trigger signal denoted as alarm trigger as "false" 30.2.
[0120] The voice audio signals may be operated simultaneously in
operations S3.5 and S3.6.
[0121] In a operation 3.5 the microphone signal V.sub.mic may be
filtered using a high-pass filter. The high-pass filter may be
limited to a desired part of the voice frequency. The filtering may
yield to a voice signal V.sub.voice.
[0122] In an operation S3.6 the voice signal may be further
filtered and processed according to the needs of the signal
processing for mobile communication systems. This processing
methods and operations are out of the scope of the present
invention.
[0123] The above described implementation of the operating steps
using a digital signal processor may not be limiting. It may also
be possible that the operations are carried out by a different
processing device. Further an electronic circuit may also enable
the processing of the operations in a comparable and appropriate
way.
[0124] According to an embodiment of the invention only few
modifications may have to be carried out to implement the
infrasonic evaluation process within a mobile phone of state of the
art. Correspondingly, a motor vehicle built-in phone may be
designed comparable to a mobile phone and therefore the description
may be also related to this phone types.
[0125] FIG. 6 shows a mobile phone with implemented infra-sound
detection according to an embodiment of the invention. The mobile
phone 300 may comprise a microphone 10, a pre-amplifier 11, an
analog-to-digital converter (ADC) 11 and a digital signal
processing unit (DSP) 12. Further a user input/output unit 5.10,
comprising a keyboard and a display, may be connected to a core
electronic 5.9 for providing input commands of the user to the core
electronic 5.9 and outputting signals and messages to inform the
user. Further the core electronic 5.9 may provide a transmission
signal (TX) due to the functions of the mobile phone which may be
amplified by amplifier 5.1 and passed to the antenna 5.11 though a
signal coupler 5.1. Received signals (RX) by the antenna 5.11 may
be passed through the signal coupler 5.2 and amplified by amplifier
5.3 to the core electronic 5.9. Audio signals, like voice signals
generated from the received signals may be passed from the core
electronic 5.9 through an amplifier 5.4 to an ear speaker 5.7.
Additionally, a buzzer 5.8 may be connected to the core electronic
5.9 through a driver 5.5 to generate indicating audio signals. The
DSP unit 200 may provide voice signals and a trigger signal to the
core electronic 5.9. The core electronic 5.9 may also provide a
signal-to-noise ratio SNR value to the DSP 200 unit.
[0126] Additionally, an optional interface 5.6 may be implemented
in the mobile phone 300. The interface 5.6 may receive the trigger
from the core electronic 5.9 and may exchange further messages
(msg) with the core electronic 5.9. The interface may also provide
interface connectors 5.61 and 5.62. The interface connector 5.61
may be a relay input/output connector and the interface connector
5.62 may be a controlling bus connector. for example to plug on a
CAN bus system. The connectors may enable to control or to transmit
a control command to an external or central alarm system.
[0127] The microphone may be adapted to detect infrasonic signals
and voice audio signals. The DSP unit 200 may provide the signal
processing for the voice signals as also the signal evaluation of
the infrasonic signals. Such an implementation according to an
embodiment of the invention of a DSP unit is described above with
respect to FIG. 5. The SNR value may be provided by the core
electronic enabling the user of the mobile phone to adapt this SNR
value to the operating conditions of the infrasonic signal
evaluation.
[0128] According to the trigger provided to the core electronic a
plurality of functions and operations may be initiated. A mobile or
built-in phone for monitoring the phone may generate a voice or
text message which may be transmitted to the respective owner, to a
security service provider, to the police or the like in response to
a trigger signal generated by the infrasonic evaluation. The
message may be a short message service (SMS) message according to
the GSM standard for mobile communication. According messages
services are provided by other mobile communication systems like
UMTS, WCDMA, DCS etc. Further, the phone may automatically call a
pre-defined number to transmit a voice message or to enable the
receiver of the call to listen to the occurrences which initiated
the trigger signal of the infrasonic evaluation, for example let
the receiver decide if the infrasonic evaluation initiated a false
or a reliable alarm.
[0129] Since an approximately position of radio frequency phone
operation according to a mobile communication system may be
determined by the provider of the mobile communication services or
another authorised provider of this service the determination of
the current position of the mobile phone may be initiated. The
initiation of the determination of the position may be initiated by
transmitting a special message of the mobile phone due to the
trigger signal to a provider 5.15.
[0130] It may be noted, that the implementation of an embodiment
according to this invention within an audio or voice processing
device may be carried out by slightly few modifications and
additions.
[0131] It is to be understood that the above described embodiment
of the invention is illustrative only, and that modifications
thereof may occur to those skilled in the art. Accordingly, this
invention is not to be regarded to be the embodiment disclosed
herein, but is to be limited only as defined by the appended
claims.
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